What are the comparative roles of reason and the passions in explaining human motivation and behaviour? Accounts of practical reason divide on this central question, with proponents of different views falling into rationalist and Humean camps. By 'rationalist' accounts of practical reason, I mean accounts which make the characteristically Kantian claim that pure reason can be practical in its issue. To reject this view is to take the Humean position that reasoning or ratiocination is not by itself capable of giving rise to a motivation to act. My own view is that the rationalist position can, in the end, be sustained against the challenge of these Humean arguments. To see why, however, it will be necessary to get clear about what is really at stake in the debate about practical reason. A further aim of my discussion will accordingly be to sharpen our understanding of the issue that divides Humeans and rationalists.